I have another question that asks for the line integral that consists of the arc of the circle x^2+y^2=4 from (2,0 to (0,2)
I know how to find the line integral, but the limits are what I'm not sure about again

x = r cos(t)
y = r sin(t)
and from the equation r = 2
x = 2 cos(t)
dx = -2sin(t)
y = 2 sin(t)
dy = 2 cos(t)
what is the value of t for the point x=2, y=0?
what is the value of t for the point x=0, y=2?